Blue Moon

[Tom Kysilko]

 From the [Minneapolis] Star Tribune:

Blue moon rises over Minnesota this weekend
July 30, 2004

If it happens once in a blue moon, you might expect it on Saturday.

That evening will bring the month's second full moon -- the currently
accepted definition of a blue moon. July's other full moon was July 2.

[Comment:  This definition is accepted by people of my acquaintance who
think about it at all; however, I believe that acceptance comes from its
repitition by newspaper, TV, and radio weather reporters over the last
several years.  OED1, M-W3, and RHUD2 do not mention this
definition.  OED1's 1525 cite has 'moon is blewe' in a counterfactual
context.  M-W3 refers (1) to a long period of time with no reference to
astronomical phenomena and (2) to the very rare occasions when the moon
appears blue due to meteorological conditions.  RHUD2 only mentions a
non-astronomical, non-meteorolical long time usage, dating it from
1815-20.  Nevertheless, the newswriter appears to have done some research,
as the sequel reveals.]

The last blue moon in these parts was on Halloween 2001; the next one will
come June 30, 2007.

Blue moon talk appears to go back several centuries. Throughout history,
some huge natural cataclysms -- volcanoes and forest fires -- have thrown
particles into the atmosphere that have actually made the moon appear blue.

By the 1800s, the occasional occurrence known as a blue moon was the fourth
full moon in a three-month season. But the term was transformed to mean the
second full moon in a calendar month by an article in an astronomy magazine
in 1946, the author of which later acknowledged having misinterpreted the
earlier meaning.

So far, he's had the last word. And under the old definition, there
wouldn't be a blue moon this year.

Bill McAuliffe
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   Tom Kysilko        Practical Data Services
   pds at visi.com       Saint Paul MN USA
           http://www.visi.com/~pds